Zarth, the Evermore

Flying
When a creature you don't control dies and is put into the graveyard, put it under your control with an additional +1/+1 counter on it at the beginning of the next end step. It is a black zombie in addition to its other types and colors.
{x}: Sacrifice a creature with converted mana cost
X. Zarth, the Evermore gains power and toughness equal to the sacrificed creature's respective power and toughness until the end of the turn.